Lead failure (set screws, subclavian crush, header, adapter, etc.) remain a major cause of inappropriate detection and therapy in patients receiving transvenous implantable cardioverter defibrillator (ICDs). Lead failure accounts for 54% of inappropriate detection due to oversensing. Lead failure typically exhibits as saturated or signal portions with high slew rates.
ICD's detect ventricular arrhythmia whenever a specific number of short depolarization intervals is reached. For example, 12 out of 16 intervals falling into the fibrillation detection interval (FDI) will trigger VF detection at which point charging is initiated. Upon charge completion, a shock is delivered. Lead failure due to fast transients in the signal, also exhibit as short depolarization intervals which are often inappropriately detected as VF resulting in reduced specificity.
Typically, broken electrodes, lead fractures, or signal saturations demonstrate as singularities (fast transients with very large slew rates, step-like transitions) on the recorded electrograms or electrocardiograms. These are usually closely coupled and short lived. What is needed is a method and apparatus that addresses these signal characteristics (sharp fast transitions that are closely coupled in time) during wavelet decomposition analysis in order to detect lead failure.